Java LinkedBlockingQueue remainingCapacity()用法及代碼示例

LinkedBlockingQueue的remainingCapacity()方法返回可以無限製添加到LinkedBlockingQueue的更多元素的數量。
返回的Thr容量出現三種情況：

如果剩餘容量為零，則不能再將其他元素添加到LinkedBlockingQueue。
如果LinkedBlockingQueue的剩餘Capacity等於Queue的大小，則無法從隊列中刪除任何元素，因為在這種情況下隊列為空。
在任何其他情況下，Capacity始終等於此LinkedBlockinQueue的初始容量和此LinkedBlockingQueue當前大小之間的差。

用法:

public int remainingCapacity()

返回值：此方法返回LinkedBlockingQueue的剩餘容量。

以下示例程序旨在說明LinkedBlockingQueue類的remainingCapacity()方法：

示例1:使用remainingCapacity()方法返回LinkedBlockingQueue的剩餘容量，其中LinkedBlockingQueue包含名稱列表。

// Java Program Demonstrate remainingCapacity() 
// method of LinkedBlockingQueue 
  
import java.util.concurrent.LinkedBlockingQueue; 
public class GFG { 
  
    public static void main(String[] args) 
    { 
        // define capacity of LinkedBlockingQueue 
        int capacityOfQueue = 7; 
  
        // create object of LinkedBlockingQueue 
        LinkedBlockingQueue<String> linkedQueue 
            = new LinkedBlockingQueue<String>(capacityOfQueue); 
  
        // Add element to LinkedBlockingQueue 
        linkedQueue.add("John"); 
        linkedQueue.add("Tom"); 
        linkedQueue.add("Clark"); 
        linkedQueue.add("Kat"); 
  
        // find remaining Capacity  of linkedQueue 
        // using remainingCapacity() method 
        int remainingCapacity = linkedQueue.remainingCapacity(); 
  
        // print result 
        System.out.println("Queue is " + linkedQueue); 
  
        // print head of queue 
        System.out.println("Remaining Capacity of Queue is "
                           + remainingCapacity); 
    } 
}

輸出：

Queue is [John, Tom, Clark, Kat]
Remaining Capacity of Queue is 3

示例2:查找包含員工列表的LinkedBlockingQueue的剩餘容量。

// Java Program Demonstrate peek() 
// method of LinkedBlockingQueue 
  
import java.util.concurrent.LinkedBlockingQueue; 
public class GFG { 
  
    public void findPeek() 
    { 
        // define capacity of LinkedBlockingQueue 
        int capacityOfQueue = 7; 
  
        // create object of LinkedBlockingQueue 
        LinkedBlockingQueue<Employee> linkedQueue 
            = new LinkedBlockingQueue<Employee>(capacityOfQueue); 
  
        // Add element to LinkedBlockingQueue 
        Employee emp1 = new Employee("Ravi", "Tester", "39000"); 
        Employee emp2 = new Employee("Sanjeet", "Manager", "98000"); 
  
        // Add Employee Objects to linkedQueue 
        linkedQueue.add(emp1); 
        linkedQueue.add(emp2); 
  
        // add element and find remaining capacity 
        // follow same process again 
        // until the queue becomes full 
  
        while (linkedQueue.size() != 7) { 
  
            // adding emp2 again and again to queue 
            System.out.println("Adding employee is success "
                               + linkedQueue.offer(emp2)); 
  
            // find remaining capacity of linkedQueue 
            // using remainingCapacity() method 
            int remain = linkedQueue.remainingCapacity(); 
  
            // print remaining capacity  value 
            System.out.println("Remaining Capacity of list :"
                               + remain); 
        } 
    } 
  
    // create an Employee Object with name, 
    // position and salary as an attribute 
    public class Employee { 
  
        public String name; 
        public String position; 
        public String salary; 
        Employee(String name, String position, String salary) 
        { 
            this.name = name; 
            this.position = position; 
            this.salary = salary; 
        } 
        @Override
        public String toString() 
        { 
            return "Employee [name=" + name + ", position="
                + position + ", salary=" + salary + "]"; 
        } 
    } 
    // Main Method 
    public static void main(String[] args) 
    { 
        GFG gfg = new GFG(); 
        gfg.findPeek(); 
    } 
}

輸出：

Adding employee is success true
Remaining Capacity of list :4
Adding employee is success true
Remaining Capacity of list :3
Adding employee is success true
Remaining Capacity of list :2
Adding employee is success true
Remaining Capacity of list :1
Adding employee is success true
Remaining Capacity of list :0

參考： https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/LinkedBlockingQueue.html#remainingCapacity–

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